I have a set of Mickey Thompson L60-15" on the back of my car. It has 10.5" of tread with a 5.5" sidewall. 10.5" equates to 266 millimeters and 5.5" is 140mm. So would this tire roughly be a 260/45 15?

Also I was wondering how well these tires would fit onto an 8" wide wheel. The Centerlines on there now are at least 9" and probably 10", I bought the car this way.

thanks